The conventional smoke detecting device, especially the photoelectric detecting device, includes a light-emitter and a light-receiver. The light-emitter emits direct light in a predetermined time period, and when there is no smoke, the signal intensity of light received by the light-receiver is the weakest. However, if smoke particles enter the inside of the photoelectric detecting device, the originally-direct light will become a scattered light due to the collision with the smoke particles. Furthermore, with the increase of smoke density, the signal intensity of light received by the light-receiver will also increase. When the signal intensity of light reaches a certain level, the photoelectric detecting device will issue an alarm signal. FIGS. 1 and 2 are respectively schematic views of conventional smoke detecting devices. However, each conventional photoelectric smoke detecting device uses only one light-receiver 12A for detection, and it is relatively sensitive to smoke particles generated during cooking, thus causing so-called false alarms. On the other hand, if the sensitivity is reduced, the alarm signal for smoke particles generated from the burning of foam materials, e.g., from furniture, will be delayed, which may negatively affect the escape and safety of personnel.
The abovementioned drawbacks of the conventional smoke detecting device seem to suggest that there is still room for improvement in the art.